Why wasn't George R.R. Martin in the final season's production of Game of Thrones?

The final season of Game of Thrones was the worst. In a matter of minutes, the entire cast of characters and plot were demolished. Martin was unable to write his book and TV episodes at the same time. The season was rushed by the creators and writers, and it did not do the book's author, George R.R Martin, justice that he did not participate in the season's production finale.